Managing Alfalfa for Yield and Quality

Alfalfa is superior to other forage crops because it is high in crude protein and energy, reducing the need for both types of supplements in feed rations. Tradeoffs do exist between forage quality, yield, and stand longevity. Proper management of fertility, pests, harvest schedule, and storage can help maximize the yield and quality of the alfalfa.

High forage yield, quality (nutritive value), and long stand life are normal goals of alfalfa producers. High forage yield can often result in low quality due to the increase in lignin. Conversely, the early harvesting required for high quality usually hastens stand decline. A reduction in lignin content as the plant ages would increase the digestibility of alfalfa, allow for a longer growing period between cuttings, increase the yield potential, and open the harvest window wider allowing for harvest timing flexibility. The advent of HarvXtra® Alfalfa with the Roundup Ready® Technology trait has caused the quality penalty to be reduced as yield increases 1. However, alfalfa without this trait loses quality as the plant continues to grow in an attempt to maximize tonnage potential. To be successful, alfalfa growers should prioritize yield, quality, and stand life for each field.

Figure 1. Delayed harvest of HarvXtra™ Alfalfa can potentially add yield without sacrificing quality. (Data comes from Forage Genetics International trials comparing HarvXtra® Alfalfa with Roundup Ready® Technology 2017 FD4 commercial varieties to commercial checks. Trials were seeded in 2013 and harvested in 2014, 2015 and 2016 in Boone, IA; Mt. Joy, PA; Nampa, ID; Touchet, WA; and West Salem, WI. Yield increase is directly correlated to the ability to delay harvest.)

Fertility Management

Alfalfa has a relatively high demand for some nutrients compared to other field crops. Monitoring the nutrient status of your soil through testing is the best way to know what nutrients are being naturally supplied and how much fertilizer is needed to keep alfalfa productive. Plant tissue analysis can help determine the nutritional status of your crop before any visual symptoms of nutrient deficiency appear. In many cases, by the time visual symptoms appear, potential yield may already be reduced. Combining tissue analysis with soil test results makes for a comprehensive nutrient management system.

Nitrogen (N). Some N (20 to 30 lbs/acre) is required for establishment of seedling alfalfa. After that, alfalfa usually gets enough N from its symbiotic relationship with Rhizobium bacteria and soil organic matter.

Phosphorus (P) and Potassium (K). Soil readings of at least 65 for P and 350 parts per million for K along with a soil pH near 7 (neutral) are considered essential for alfalfa production. A neutral soil pH is needed so Rhizobium can fix N for use by alfalfa plant. Yield potential of alfalfa will be reduced and/or stand life shortened if these essential nutrients are inadequate or soil pH is less than 6.5.

Sulfur (S). Soils may become deficient in Sulfur in some regions, especially if no manure has been applied in the last two years. The need for S should be verified with tissue sampling, as soil sampling will not accurately predict Sulfur requirements.

Pest Management

Using integrated pest management practices for weeds, diseases, and insects can help protect yield potential and forage quality. Consult University Extension specialists in your area for local management recommendations for specific pests.

Harvest Management

The intensity of cutting management (number of cuttings per year) should be based on the desired quality and life expectancy of the alfalfa stand. Alfalfa producers who want to harvest based on forage quality should pay close attention to harvesting on time, especially the first cutting. One method to monitor the growth stage of first cutting alfalfa is the PEAQ (predictive equations for alfalfa quality) stick method. The PEAQ stick uses both alfalfa stem height and maturity to predict forage quality. Being able to distinguish alfalfa growth stages (vegetative, early bud, mid-bud, late bud, early bloom, and full bloom) to accurately assess alfalfa quality is necessary.

After the first harvest, for dairy production systems, cuttings are usually on a 28-day schedule. In beef systems, cutting is usually delayed until about 10% bloom to maximize yield but maintain a quality suitable for beef production. Cut height is an additional harvest consideration. The general recommendation is a cut height of 2 to 3 inches, except for the final cutting height, where a 4-inch height is recommended in northern areas to help catch and hold snow. Research has shown that for varieties that do not have the HarvXtra® trait, every 1-inch reduction in cutting height results in a 0.5 ton/acre increase of dry matter over the course of the season. However, quality decreased by about 4 relative feed value units for each cutting.2

Wider harvest swaths can help speed drying time, which can help decrease dry matter loss in the field and result in improved quality. A wider swath can reach 65% moisture in 5 to 8 hours, allowing haylage harvest the same day. Minimizing wheel tracks can help reduce yield losses for successive cuttings.

Storage

Storing hay inside a building helps minimize dry matter losses from 1 to 5% (Table 1). Hay that is in contact with soil and left uncovered can lose up to 50% dry matter after 1 year. Even if covered, contact with soil can result in a 15% loss. Moisture can be kept from wicking from the ground with the use of plastic wrap, large crushed stone, ties and/or poles, pallets, or tires.3 For more information, please reference the American Society of Agronomy Alfalfa Management Guide at https://www.agronomy.org/files/publications/alfalfa-management-guide.pdf.

Sources:

1Combs, D. 2016. Low-lignin alfalfa varieties offer potential quality gains. Hay & Forage Grower®. hayandforage.com/article-490-low-lignin-alfalfa-varieties-offer-potential-quality- gains.html

2Wiersma, R.W. and Wiederholt, R. Alfalfa cutting height to maximize forage yield and quality. https://fyi.uwex.edu.

3Holmes, B. Dry round hay bale storage costs. https://fyi.uwex.edu.

Other sources include: Undersander, D., Cosgrove, D., Cullen, E., et al. 2011. Alfalfa management guide. American Society of Agronomy. http://www.agronomy.org. Web sources verified 7/5/18.

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